1. Field of the Invention
The present invention relates to receivers and, more particularly, to a receiver which can perform tuning within a tuning band width related to a signal frequency band width for television broadcast.
2. Description of the Related Art
The signal frequencies of television broadcast lie within a band width largely different from that of the signal frequencies of radio broadcast. That is, almost all the television broadcast signals falls under a frequency band width of 6 MHz, whereas the radio broadcast signals are in a frequency band width as narrow as approximately 100 kHz. As a result, it has been a conventional practice to separately provide receivers for processing television and radio broadcast signals. In order to receive VHF television broadcasts, a television broadcast receiver 1a was required to include, as shown in FIG. 5, an input tuning circuit 2a, an RF amplifier 3a, an inter-stage tuning circuit 4a, a mixer 5a, a tuning circuit 6a, a local oscillation circuit 8a and an IF amplifier 7a. For receiving FM radio broadcast, a radio broadcast receiver 1b shown in FIG. 6 was required to have the similar circuits 2b-8b. 
This however necessitate two circuits for each of signal processing, such as in tuning circuits and frequency conversion circuits, thus posing a problem of high cost.
Therefore, it is a primary object of the present invention to provide a receiver which can receive both television broadcast and radio broadcast.
A receiver according to the present invention, comprises: a tuning circuit having a first tuning band width; a first input terminal for inputting a first broadcast signal having a first frequency band width correlated to the first tuning band width; second input terminal for inputting a second broadcast signal having a second frequency band width narrower than the first frequency band width; an attenuation circuit for attenuating signal components of the second broadcast signal at around a desired channel; and a selection circuit for selecting and inputting to the tuning circuit one of the first broadcast signal and the second broadcast signal attenuated in the signal components.
According to this invention, inputted through the first terminal a first broadcast signal possessing a first frequency band width related to a first tuning band width while inputted through the second terminal a second broadcast signal having a second frequency band width narrower than the first tuning band width. The selection circuit selects one of the first broadcast signal and the second broadcast signal attenuated in signal components, and inputs it to the tuning circuit having a first tuning band width.
In one embodiment of the present invention, the attenuation circuit attenuates the signal components over the first frequency band width except for at the desired channel. Incidentally, the attenuation circuit includes a resonant circuit which resonates at frequency correlated to a tuning voltage.
In another embodiment of the present invention, the first broadcast signal is a television signal to be broadcast in a VHF band range, and the second broadcast signal is a radio signal to be FM broadcast in the VHF band range.
According to this invention, because attenuation is made for the second broadcast signal on signal components over the channel close to a desired channel, the second broadcast signal can be properly received even where the tuning means is broad in tuning band width. That is, proper reception is possible for both the first broadcast signal and the second broadcast signal.